For the inspection, maintenance and renovation of duct systems, for example, sewage duct systems, controllable self-propelled robots are usually used, which are capable of performing the required measurement processes or mechanical renovation work. For this purpose, the robots usually have a camera system for visualizing the state of the duct. For example, if a sewage duct is not airtight at a certain location, then a tubular liner can be pulled in, which can be, for example, impregnated with epoxy resin and which therefore cures rapidly. If such liners are pulled in, then it is necessary to again open up duct branches, house connections and the like, which at first are closed by the tubular liner, after the curing. For this purpose, the exact position and size of the closed branch obviously have to be known. In order to determine the position of branches before closing with the tubular liner, the conventional approach is to measure the distance of a branch from a reference site using a mechanical length measurement device attached to the self-propelled robot. In the simplest case, this can be simply a kind of measuring tape.
Naturally, the most exact possible position determination is not required only in the case of the above described renovation case. In fact, for certain features within a duct or duct system, or very generally for any pipeline or any pipeline system, it is often desirable to determine the associated positions. In addition to the already mentioned branches, such features of interest can be bends, diameter changes or (annular) slits, for example.
However, the determination of the position associated with a certain feature of the duct system using a mechanical length measurement system is expensive and prone to error.
Therefore, the present invention is based on the problem of creating a method and an apparatus with which at least the position of a feature of interest of a pipeline or of a pipeline system can be determined reliably, rapidly and cost effectively with the simplest means possible.